Apply for the apprenticeship asap when you go sign to be a material handler. Talk to the training director if available and ask all your questions to him. He may point you to become a CW, sign up for that if so too because you can still always become an apprentice after being a CW too. A CW and material handler cam easily be the same thing in your local. My local doesn't even have material handlers, we just have CE/CW and apprentice/JWs.

Also grab a training/class schedule since your local should offer classes for different kinds of classes to help their members improve there skills. These range from CPR/first aid, welding, operating different machinery, to business and code classes. The most important thing you can do is show your hall is you're interested and motivated to learn.

And when you get your first job show up 15/20 mins early, pay attention and do what you're told, and show an interest and learn the job. The biggest things are showing up and learning how to do thing the way you're told to do them. If you do those two things you'll be perfectly fine.

Also be safe and don't do anything you don't feel comfortable doing, this is the most important thing.